Abstract

A previously well 30 year old man presented with a short history of intra-articular mechanical locking, swelling, and anteromedial joint line pain. There was localised tenderness, and McMurray’s test was positive. Arthroscopy revealed a 3.6 × 2.6 × 1.5 cm firm pedicular localised pigmented villonodular synovitis originating from the insertion of the anterior horn of the medial meniscus. Owing to its size and consistency, mini-arthrotomy was required. This allowed a return to sporting activities. Localised pigmented villonodular synovitis can mimic symptoms of a meniscal tear.

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Knee problems account for a large portion of physiotherapy and orthopaedic practice. Clinical history and good examination are of paramount importance. Many problems require no intervention and settle. Meniscal injury and tears of the anterior cruciate ligament are common, and a variety of surgical techniques have been described for their management. Radiological investigation and arthroscopy further assist in diagnosis, and the problem may be amenable to treatment at the same sitting.

Meniscal tears typically affect those under the age of 40, following a twisting knee injury in flexion. Patients present with various symptoms and signs, typically joint line pain and tenderness, locking, and quadriceps wasting.

We describe the case history of a physically active man with a seemingly straightforward meniscal tear. We discuss localised pigmented villonodular synovitis (LPVNS) and highlight the importance of remembering this differential diagnosis in the sportsperson.

CASE REPORT

We present the case of a fit 30 year old man who was a regular weekly sportsman. During a game of football, there were a number of twisting episodes associated with pain. He was able to complete the match, but subsequently the knee swelled and became increasingly uncomfortable. Symptoms failed to settle with rest and protected mobilisation. Periods of locking and recurrent swelling with pain remained a regular feature. On examination there was specific anteromedial joint line pain. McMurray’s test was positive with a painful clunk. Radiographs were normal. A diagnosis of a medial meniscal tear was made.

Arthroscopy, however, revealed a large (3.6 × 2.6 × 1.5 cm) pedicular lesion originating from the insertion of the anterior horn of the medial meniscus (fig 1). Owing to its size and firmness, it was safest to perform a mini-arthrotomy (fig 2). Histological examination confirmed a pigmented villonodular synovitis (PVNS). Excision led to immediate resolution of symptoms and a rapid return to sporting activities.

DISCUSSION

Although PVNS usually affects the knee,1–14 it is not common. The arthroscopic incidence is estimated to be 1 in 250, with a yearly incidence of 1.8 cases per million population.1 A quarter of these are of the localised form.1

Original descriptions date back to Chassaignac 150 years ago.11 A diffuse form in the knee was reported in 1909, with the term PVNS finally adopted by Jaffe et al in 1941.2

It can be diffuse or localised as a pedicular lesion typically anteromedial from the meniscocapsular junction. Features are typically mechanical with localised pain.2–9,13 Recurrence is a reported problem with the diffuse form of PVNS. Only two cases of recurrence of the local variety have been reported.11,15

Our patient had a short history in relation to symptoms. The convincing intra-articular features prompted the early arthroscopy, otherwise magnetic resonance imaging would have been a useful diagnostic tool. The size of the lesion and it resilience precluded piecemeal removal. Hence the arthroscopy portal was enlarged sufficiently to allow visualisation of the base and safe removal. Indeed a safe mini-arthrotomy is better than a poorly performed arthroscopy.

Take home message

LPVNS can mimic symptoms of meniscal injury.

Although it is uncommon, we emphasise the importance of remembering any differential diagnoses when dealing with any seemingly straightforward injury. LPVNS affecting the knee can be detected by magnetic resonance imaging15 or arthroscopy. Open excision, however, may be necessary for large firm lesions to allow safe and complete removal.

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